Time comparison device and time quality monitoring method

Abstract

[Problem] An object is to obtain a time quality of another GM with high accuracy on the basis of a GM a time quality of which is known already.[Solution] A first TC 20 includes a time comparison unit 23 that calculates time difference information by comparing first time information of a first PTP processing unit 12 and second time information of a second PTP processing unit 22 with each other. In addition, a quality calculation device 5 measures time difference information until time difference information obtained by a time comparison unit 23 of the first TC 20 and time difference information obtained by a time comparison unit 43 of a second TC 40 match each other, and obtains a GM time quality of a second GM 30 on the basis of a transmission time error of the time transmission network 2 at a timing when both of pieces of the time difference information match each other.

The invention claimed is: 
     
       1. A time comparison device configured to monitor a time quality of a second grand master located on a host device side of a time transmission network through the time transmission network from a first grand master located on an opposite side of the time transmission network, the time comparison device comprising:
 a first time synchronization unit, including one or more processors, configured to accept synchronization of first time information from the first grand master by receiving a first time synchronization packet from the first grand master through the time transmission network; 
 a second time synchronization unit, including one or more processors, configured to accept synchronization of second time information from the second grand master by receiving a second time synchronization packet from the second grand master without passing through the time transmission network; 
 a time comparison unit, including one or more processors, configured to calculate time difference information by comparing the first time information and the second time information with each other; and 
 a quality calculation unit, including one or more processors, configured to: determine that i) the time difference information obtained by the time comparison unit on the host device side and ii) another time difference information obtained by another time comparison unit of another time comparison device on the opposite side match each other, and 
 in response to determining that i) the time difference information and ii) the another time difference information match each other, to obtain a time quality of the second grand master based on a) a transmission time error of the time transmission network at a timing when both the time difference information and the another time difference information match each other and b) a time quality of the first grand master. 
 
     
     
       2. The time comparison device according to  claim 1 , wherein
 the time comparison unit is configured to measure the time difference information and the another time difference information a plurality of times within a predetermined period of time, and 
 the quality calculation unit is configured to obtain the time quality of the second grand master when statistical values of i) the time difference information and ii) the another time difference information measured a plurality of times match each other. 
 
     
     
       3. A time quality monitoring method performed by a time comparison device configured to monitor a time quality of a second grand master located on a host device side of a time transmission network through the time transmission network from a first grand master located on an opposite side of the time transmission network, the time comparison device including a first time synchronization unit including one or more processors, a second time synchronization unit including one or more processors, a time comparison unit including one or more processors, and a quality calculation unit including one or more processors, the time quality monitoring method comprising:
 by the first time synchronization unit, accepting synchronization of first time information from the first grand master by receiving a first time synchronization packet from the first grand master through the time transmission network; 
 by the second time synchronization unit, accepting synchronization of second time information from the second grand master by receiving a second time synchronization packet from the second grand master without passing through the time transmission network; 
 by the time comparison unit, calculating time difference information by comparing the first time information and the second time information with each other; and 
 by the quality calculation unit, determining that i) the time difference information obtained by the time comparison unit on the host device side and ii) another time difference information obtained by another time comparison unit of another time comparison device on the opposite side match each other, and in response to determining that i) the time difference information and ii) the another time difference information match each other, obtaining a time quality of the second grand master based on a) a transmission time error of the time transmission network at a timing when both the time difference information and the another time difference information match each other and b) a time quality of the first grand master. 
 
     
     
       4. The time quality monitoring method according to  claim 3 , further comprising:
 by the time comparison unit, measuring the time difference information and the another time difference information a plurality of times within a predetermined period of time; and 
 by the quality calculation unit, obtaining the time quality of the second grand master when statistical values of i) the time difference information and ii) the another time difference information measured a plurality of times match each other.